Exercise system



FIG. 1 is a front perspective view of the exercise system showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof; and,

FIG. 6 is a bottom view thereof.

The broken lines represent portions of the exercise system which form no part of the claimed design. 

CLAIM The ornamental design for an exercise system, as shown and described. 